[Octave-bug-tracker] [bug #56069] [octave forge] (symbolic) Laplace transform of sin(w*t) gives wrong value

[Mike Miller]

Update of bug #56069 (project octave):

                 Summary: Symbolic Laplace transform of sin(w*t) gives wrong
value => [octave forge] (symbolic) Laplace transform of sin(w*t) gives wrong
value

    _______________________________________________________

Follow-up Comment #1:

It's nothing special about the variable 'w', but it's about the sorting order
of the variables. When you pass an expression instead of a function as the
first argument, the 'symvar' function is used to extract the variable that is
closest to 'x'. I think this is a Matlab compatibility thing. @cbm is that
right?

So for the expressions 'sin(a*t)' and 'sin(b*t), 't' is chosen as the
independent variable that the Laplace transform is computed over. But for
'sin(w*t)', 'w' is chosen instead of 't'.

One example way to work around this is to define the expression as a function
of t:


>> f(t) = sin(w*t);
>> laplace (f)
ans = (sym)

     w   
  ───────
   2    2
  s  + w 



    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?56069>

_______________________________________________
  Message sent via Savannah
  https://savannah.gnu.org/